Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
import sys
input = sys.stdin.readline
from collections import deque
H, W = map(int, input().split())
X = [1,0,-1,0]
Y = [0,-1,0,1]
num = 0
D = []
for i in range(H):
  s = list(input())
  num += s.count(".")
  D.append(s)
Q = deque()
Q.append((0,0))
dist = [[-1]*W for i in range(H)]
dist[0][0] = 0

while Q:
  y,x = Q.popleft()
  for i in range(4):
    nx = x + X[i]
    ny = y + Y[i]
    if 0 <= nx < W and 0 <= ny < H and dist[ny][nx] == -1 and D[ny][nx] == ".":
      dist[ny][nx] = dist[y][x] + 1
      Q.append((ny,nx))

if dist[H-1][W-1] == -1:
  print(-1)
else:
  print(num-dist[H-1][W-1]-1)